Pictures in time: Study tracks Lake Superior erosion
 o help local governments plan and manage shoreline
development, a group of UW-Madison civil and environmental engineers
is characterizing the state of erosion along the Wisconsin shoreline
of Lake Superior. “People often build their homes too close to
the edge of a bluff, not realizing they are living in a highly active
environment,” says Professor
Tuncer Edil. “Homes and cabins are often lost to bluff recession
or need to be relocated further from the bluff edge. This often happens
at the expense of the owner and taxpayers.”
The group, which includes Edil, Assistant
Professor Chin Wu, Geology and Geophysics Professor David Mickelson,
and research assistant Mike Swenson, hopes to estimate how much bluff
recession will occur within the next 50 years if lake levels change—for
example, as a result of global warming.
To learn more, the researchers turned to the lake
itself, surveying the entire shoreline to characterize its current state
of erosion. Then they compared those results with historical air photos
to measure how far Lake Superior bluffs have retreated during the past
30 years.
During large storms, they measured how far waves
rushed onto the lake’s beaches to determine how the waves interact
with the beach and whether they also crashed into the lake’s bluffs.
“We used historical wave data to determine how much wave energy
reaches bluffs with different characteristics along the shoreline,”
says Edil. “We also measured historical bluff recession and have
shown that bluff recession is related to this measurement of wave energy.”
The correlation, he says, enables the researchers
to predict erosion based on wave characteristics reflecting climatic
factors.
Armed with its results, group members have attended
public outreach programs to discuss the effects of bluff recession with
people living along the shoreline. In addition, they have attended workshops
with county planners who hope to use the group’s research results
immediately for issuing building permits on coastal properties. “Currently,
work is being performed to present our work to the public and implement
our research in zoning ordinances along the Wisconsin shoreline of Lake
Superior,” says Edil.
With individual studies of the relationships between
wave energy and erosion, the research could apply to other large water-body
erosion situations, he says. Ultimately, it will enable local governments
to establish shoreline zoning ordinances—and the knowledge will
help builders determine safe setback distances for the lake homes they
build.
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